Multi-electrode assembly for an implantable medical device

ABSTRACT

A method, system, and apparatus are provided for an electrode assembly comprising a plurality of electrodes for use with an implantable medical device for conducting an electrical signal between the implantable medical device and a target tissue. The electrode assembly includes a helical member and first and second electrodes formed upon the helical member. The first and second electrodes are adapted to deliver the electrical signal. The electrode assembly also includes a first conductive element formed upon the helical member and operatively coupled to the first electrode. The electrode assembly also includes a second conductive element formed upon the helical member and operatively coupled to the second electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to implantable electrode assemblies,and more particularly to an electrode assembly comprising a plurality ofelectrodes organized into a helical structure. The electrodes may beoperatively coupled to an implantable medical device (IMD).

2. Description of the Related Art

As used herein, “stimulation” or “stimulation signal” refers to theapplication of an electrical, mechanical, magnetic, electro-magnetic,photonic, audio and/or chemical signal to a neural structure in thepatient's body. The signal is an exogenous signal that is distinct fromthe endogenous electrical, mechanical, and chemical activity (e.g.,afferent and/or efferent electrical action potentials) generated by thepatient's body and environment. In other words, the stimulation signal(whether electrical, mechanical, magnetic, electro-magnetic, photonic,audio or chemical in nature) applied to the nerve in the presentinvention is a signal applied from an artificial source, e.g., aneurostimulator.

A “therapeutic signal” refers to a stimulation signal delivered to apatient's body with the intent of treating a disorder by providing amodulating effect to neural tissue. The effect of a stimulation signalon neuronal activity is termed “modulation”; however, for simplicity,the terms “stimulating” and “modulating”, and variants thereof, aresometimes used interchangeably herein. In general, however, the deliveryof an exogenous signal itself refers to “stimulation” of the neuralstructure, while the effects of that signal, if any, on the electricalactivity of the neural structure are properly referred to as“modulation.” The effect of delivery of the stimulation signal to theneural tissue may be excitatory or inhibitory and may potentiate acuteand/or long-term changes in neuronal activity. For example, the“modulating” effect of the stimulation signal to the neural tissue maycomprise one or more of the following effects: (a) changes in neuraltissue to initiate an action potential (afferent and/or efferent actionpotentials); (b) inhibition of conduction of action potentials (whetherendogenous or exogenously induced) or blocking the conduction of actionpotentials (hyperpolarizing or collision blocking), (c) affectingchanges in neurotransmitter/neuromodulator release or uptake, and (d)changes in neuro-plasticity or neurogenesis of brain tissue.

Thus, electrical neurostimulation or modulation of a neural structurerefers to the application of an exogenous electrical signal (as opposedto mechanical, chemical, photonic, or another mode of signal delivery)to the neural structure. Electrical neurostimulation may be provided byimplanting an electrical device underneath the skin of a patient anddelivering an electrical signal to a nerve such as a cranial nerve. Inone embodiment, the electrical neurostimulation involves sensing ordetecting a body parameter, with the electrical signal being deliveredin response to the sensed body parameter. This type of stimulation isgenerally referred to as “active,” “feedback,” or “triggered”stimulation. In another embodiment, the system may operate withoutsensing or detecting a body parameter once the patient has beendiagnosed with a medical condition that may be treated byneurostimulation. In this case, the system may periodically apply aseries of electrical pulses to the nerve (e.g., a cranial nerve such asa vagus nerve) intermittently throughout the day, or over anotherpredetermined time interval. This type of stimulation is generallyreferred to as “passive,” “non-feedback,” or “prophylactic,”stimulation. The stimulation may be applied by an implantable medicaldevice that is implanted within the patient's body. In anotheralternative embodiment, the signal may be generated by an external pulsegenerator outside the patient's body, coupled by an RF or wireless linkto an implanted electrode.

Generally, neurostimulation signals that perform neuromodulation aredelivered by the implantable device via one or more leads. The leads aregenerally coupled at a distal end to electrodes, which are coupled to atissue in the patient's body. Multiple leads/electrodes may be attachedto various points of a nerve or other tissue inside a human body fordelivery of neurostimulation. Generally, each lead is associated with aseparate electrode, particularly when each of the electrodes is intendedto perform a different function (e.g., deliver a first electricalsignal, deliver a second electrical signal, sense a body parameter,etc.).

Generally, a single electrode is associated with each lead originatingfrom the IMD. The number of leads that originate from the IMD is limiteddue to the size constraints of the IMD and of the patient's body.Therefore, a limited number of electrodes using state-of-the-arttechnology can be used to deliver electrical stimulation from an IMD.

Further, state-of-the-art medical systems call for performing astimulation during a time period that is separate from a time period ofperforming a sensing function for sensing the patient's biologicalsignals. Further, a first lead associated with a first electrode maydeliver a therapeutic electrical signal, while a second lead associatedwith a second electrode may perform data acquisition for sensing ofvarious biometric parameters in the patient's body. This process may beinefficient since the state-of-the-art generally lacks a system forsimultaneously delivering an electrical signal to a neural structure andsensing electrical activity, particularly where associated with theneural structure to which the signal is applied. Further, problems withthe state-of-the-art also include a limitation on the number ofelectrodes that may be employed by an IMD to deliver various stages oftherapy and/or sensing functions.

The present invention is directed to overcoming, or at least reducing,the effects of one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an electrode assemblycomprising a plurality of electrodes for use with an implantable medicaldevice for conducting an electrical signal between the implantablemedical device and a target tissue. The electrode assembly includes ahelical member having a first and a second electrode formed upon thehelical member. The first and second electrodes are adapted to deliverthe electrical signal. The electrode assembly also includes a firstconductive element formed upon the helical member and operativelycoupled to the first electrode. The first conductive element is adaptedto carry the electrical signal to the first electrode. The electrodeassembly also includes a second conductive element formed upon thehelical member and operatively coupled to the second electrode.

In yet another aspect, the present invention includes a method forforming a helical electrode assembly for carrying an electrical signalassociated with an implantable medical device. A first layer is formedon a generally flat substrate. In one embodiment, the substrate isgenerally planar. A first conducting structure is formed upon the firstlayer. The first conducting structure includes a first electrode and afirst lead operatively coupled to the first electrode. A second,non-conductive layer is formed above the first layer. A secondconducting structure is formed upon the second, non-conductive layer.The second conducting structure includes a second electrode and a secondlead operatively coupled to the second electrode. The method furtherincludes the step of forming the generally flat substrate into a helicalstructure.

In another aspect, the present invention includes another method forforming a helical electrode assembly for carrying a signal associatedwith an implantable medical device. A first layer is formed on agenerally flat substrate. A first conducting structure and a secondconducting structure are formed upon the first layer. The firstconducting structure includes a first electrode and a first leadoperatively coupled to the first electrode. The second conductingstructure includes a second electrode and a second lead operativelycoupled to the second electrode. A second, non-conductive layer isformed such that the first and second leads are substantially covered bythe second layer and the first and second electrodes remain exposed. Themethod also comprises the step of forming the generally flat substrateand first and second layers into a helical structure.

In yet another aspect, the present invention provides an implantablemedical system for providing a therapeutic electrical signal to a targettissue using a helical electrode assembly. The system of the presentinvention includes an implantable medical device for generating atherapeutic electrical signal. The system also includes a lead assemblyoperatively coupled to the implantable medical device and adapted tocarry the therapeutic electrical signal. The lead assembly comprisesfirst and second lead elements. The system also includes an electrodeassembly operatively coupled to the lead assembly. The electrodeassembly includes a helical member having first and second electrodesformed thereon. The electrode assembly also includes a first conductiveelement formed upon the helical member and operatively coupled to thefirst electrode and to the first lead element. The electrode assemblyalso includes a second conductive element formed upon the helical memberand operatively coupled to the second electrode and to the second leadelement. The first and second electrodes are adapted to deliver theelectrical signal to tissue of a patient when coupled thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 is a stylized diagram of an implantable medical device implantedinto a patient's body for providing stimulation to a portion of thepatient's body, in accordance with one illustrative embodiment of thepresent invention;

FIG. 2 illustrates a stylized isometric illustration of an electrodeassembly in accordance with one embodiment of the present invention;

FIG. 3 illustrates another isometric depiction of the electrode assemblyand an electrode in accordance with one illustrative embodiment of thepresent invention;

FIG. 4 illustrates a stylized depiction of the electrode assembly ofFIGS. 2 and 3 during fabrication, in accordance with the illustratedembodiment of the present invention;

FIG. 5 illustrates a flowchart associated with a method for providingthe electrode assembly of FIGS. 2-4, in accordance with an illustrativeembodiment of the present invention, is provided;

FIG. 6 illustrates a stylized depiction of the electrode assembly of thepresent invention in a staggered multi-layered configuration, inaccordance with an illustrative embodiment of the present invention;

FIG. 7 illustrates a stylized side view of a flexible material uponwhich a first through third layers and corresponding conductivestructures are formed, in accordance with an illustrative embodiment ofthe present invention; and

FIG. 8 illustrates an alternative stylized depiction of the electrodeassembly of the present invention in a multi-layered configuration, inaccordance with an illustrative embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrative embodiments of the invention are described herein. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. In the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the design-specific goals, which will vary from oneimplementation to another. It will be appreciated that such adevelopment effort, while possibly complex and time-consuming, wouldnevertheless be a routine undertaking for persons of ordinary skill inthe art having the benefit of this disclosure.

Certain terms are used throughout the following description and claimsrefer to particular system components. This document does not intend todistinguish between components that differ in name but not function. Inthe following discussion and in the claims, the terms “including” and“includes” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to.” Also, the term“couple” or “couples” is intended to mean either a direct or an indirectelectrical connection. “Direct contact,” “direct attachment,” orproviding a “direct coupling” indicates that a surface of a firstelement contacts the surface of a second element with no substantialattenuating medium therebetween. The presence of substances, such asbodily fluids, that do not substantially attenuate electricalconnections does not vitiate direct contact. The word “or” is used inthe inclusive sense (i.e., “and/or”) unless a specific use to thecontrary is explicitly stated.

As used herein, “stimulation” or “stimulation signal” refers to theapplication of an electrical, mechanical, and/or chemical signal to aneural structure in the patient's body. In one embodiment, thestimulation comprises an electrical signal. The stimulation signal mayinduce afferent and/or efferent action potentials on the nerve, mayblock native afferent and/or efferent action potentials, or may beapplied at a sub-threshold level that neither generates actionpotentials nor blocks native action potentials.

The stimulation signal applied to the neural structure in embodiments ofthe present invention refers to an exogenous signal that is distinctfrom the endogenous electrical, mechanical, and chemical activity (e.g.,afferent and/or efferent electrical action potentials) generated by thepatient's body and environment. In other words, the stimulation signal(whether electrical, mechanical or chemical in nature) applied to thenerve in the present invention is from an artificial source, e.g., aneurostimulator.

The term “electrode” or “electrodes” described herein may refer to oneor more stimulation electrodes, one or more sensing electrodes, and/orto one or more electrodes that are capable of delivering a stimulationsignal as well as performing a sensing function. Stimulation electrodesmay refer to an electrode that is capable of delivering a stimulationsignal to a tissue of a patient's body. A sensing electrode may refer toan electrode that is capable of sensing a physiological indication of apatient's body. “Electrode” and/or “electrodes” may also refer to one ormore electrodes capable of delivering a stimulation signal as well assensing a physiological indication.

The terms “stimulating” and “stimulator” may generally refer to deliveryof a stimulation signal to a neural structure. The effect of suchstimulation on neuronal activity is termed “modulation”; however, forsimplicity, the terms “stimulating” and “modulating”, and variantsthereof, are sometimes used interchangeably herein. In general, however,the delivery of an exogenous signal refers to “stimulation” of theneural structure, while the effects of that signal, if any, on theelectrical activity of the neural structure are properly referred to as“modulation.” In one embodiment of the present invention, methods,apparatus, and systems are provided involving a helical electrode tostimulate an autonomic nerve, such as a cranial nerve, e.g., a vagusnerve, using an electrical signal to treat a medical condition such asepilepsy and other movement disorders, mood and other neuropsychiatricdisorders, dementia, coma, migraine headache, obesity, eating disorders,sleep disorders, cardiac disorders (such as congestive heart failure andatrial fibrillation), hypertension, endocrine disorders (such asdiabetes and hypoglycemia), and pain, among others. A generally suitableform of neurostimulator for use in the method and apparatus of thepresent invention is disclosed, for example, in U.S. Pat. No. 5,154,172,assigned to the same assignee as the present application. Theneurostimulator may be referred to a NeuroCybernetic Prosthesis (NCP®,Cyberonics, Inc., Houston, Tex., the assignee of the presentapplication). Certain parameters of the electrical stimulus generated bythe neurostimulator are programmable, such as be means of an externalprogrammer in a manner conventional for implantable electrical medicaldevices.

Embodiments of the present invention provide for an electrode assemblycomprising a plurality of individual electrodes or an array ofelectrodes. The electrode assembly may be formed as a helical structure,wherein the electrode assembly may comprise a plurality of electrodesand associated conductive elements for delivering various electricalstimulation signals. One or more of the plurality of electrodesassociated with the electrode assembly may also provide for the capacityto perform sensing. Therefore, substantially simultaneous delivery ofstimulation and the acquisition of sensing signals may be performedutilizing the electrode array of the electrode assembly of the presentinvention. The term “electrode array” may refer to two or moreelectrodes residing on a single electrode assembly.

Embodiments of the present invention provide a flexible “ribbon-type”material upon which various electrodes may be provided in a variety ofconfigurations to provide efficient delivery of therapy and/or sensingfunctions. For example, electrodes may be positioned on a helical membersuch that successive electrodes are generally linear along an axis of anerve, such as the vagus nerve. Alternatively, various electrodes on theelectrode assembly of the present invention may be positioned in astaggered fashion to deliver a signal in a particular geometry orconfiguration to target portions of a nerve. An electrode assembly maybe employed using a state-of-the-art IMD such that a number ofelectrodes may be substantially simultaneously activated, oralternatively, activated in a staggered or sequential fashion.

Embodiments of the present invention also provide for a method formanufacturing an electrode assembly that comprises a plurality ofelectrodes. A non-conductive material may be coated with various layersof conductive and non-conductive films or layers to create variousconductive structures, such as electrodes, strips of conductivematerials that provide electrical signals to the electrodes, andinterfaces that provide connection between the various electrodes on theelectrode assembly and lead(s) that are in operative communication withthe IMD. For example, photolithography processes may be used on aplurality of layers formed on a substrate to provide various electrodesthat are situated at desirable or strategic locations on a singleelectrode assembly, which may be formed into a helical configuration.This helical configuration may be used to wrap the electrode assemblyaround various portions of a patient's body, such as a nerve, such thatthe multiple electrodes may come into contact at desired locations of aparticular nerve in a desired geometry or configuration. One or more ofthe multiple electrodes may be energized in a strategically timedfashion to provide desired stimulation to a portion of a patient's body.This may provide the ability to direct or steer current flow to apre-determined position and direction, through a portion of a patient'sbody, such as a nerve. Utilizing embodiments of the present inventionmore efficient and effective delivery of stimulation may be realized.

Although not so limited, a system capable of implementing embodiments ofthe present invention is described below. FIG. 1 depicts a stylizedimplantable medical system 100 for implementing one or more embodimentsof the present invention. FIG. 1 illustrates an electrical signalgenerator 110 having main body 112 comprising a case or shell 121 with aheader 116 for connecting to leads 122. The generator 110 is implantedin the patient's chest in a pocket or cavity formed by the implantingsurgeon just below the skin (indicated by a dotted line 145), similar tothe implantation procedure for a pacemaker pulse generator.

A nerve electrode assembly 125, preferably comprising a plurality ofelectrodes, is conductively connected to the distal end of an insulated,electrically conductive lead assembly 122, which preferably comprises aplurality of lead wires (one wire for each electrode). Each electrode inthe electrode assembly 125 may operate independently or alternatively,may operate in conjunction with each other to form a cathode and ananode. The electrode assembly 125 illustrated in FIG. 1 may be formedinto a helical structure that comprises a plurality of electrodes on aninside surface of the helical structure to deliver electrical signalsvia the plurality of electrodes in a simultaneous or time-delayedfashion, as well as perform efficient sensing of electrical signals in apatient's body.

Lead assembly 122 is attached at its proximal end to connectors on theheader 116 on case 121. The electrode assembly 125 at the distal end oflead assembly 122 may be surgically coupled to a target tissue such asvagus nerve 127. The electrical signal may also be applied to othercranial nerves. The electrode assembly 125 preferably comprises abipolar stimulating electrode pair, or may comprise three, four or evenmore electrodes. The electrode assembly 125 is preferably wrapped aroundthe target tissue, such as a vagus nerve. Prior art electrodes have beenprovided that wrap around a target tissue, such as the electrode pairdescribed in U.S. Pat. No. 4,573,481. In the prior art structures,however, a separate helical element is provided for each electrode. Incontrast, the present invention involves a plurality of electrodes on asingle helical element. Varying lengths of the helical element may beprovided, depending upon the pitch of the helix and the number ofelectrodes thereon. Lengths may range from 3 mm to 50 mm, although evensmall or longer helices may be employed in particular applications. Leadassembly 122 may be secured, while retaining the ability to flex withmovement of the chest and neck, by a suture connection to nearby tissue.

In one embodiment, the open helical design of the electrode assembly 125is self-sizing and flexible, minimizes mechanical trauma and allows bodyfluid interchange with the target tissue. The electrode assembly 125preferably conforms to the shape of the target tissue, providing a lowstimulation threshold by allowing a large stimulation contact area.Structurally, the electrode assembly 125 comprises a plurality ofelectrode ribbons (not shown), of a conductive material such as preciousmetals and/or alloys and oxides thereof, including platinum, iridium,platinum-iridium alloys, and/or oxides of the foregoing. The electroderibbons are individually bonded to an inside surface of an elastomericbody portion, which may comprise a helical assembly. The lead assembly122 may comprise two distinct lead wires or a multi-wire cable whoseconductive elements are respectively coupled to one of the conductiveelectrode ribbons. The elastomeric body portion is preferably composedof silicone rubber, or another biocompatible, durable polymer such assiloxane polymers, polydimethylsiloxanes, polyurethane, polyetherurethane, polyetherurethane urea, polyesterurethane, polyamide,polycarbonate, polyester, polypropylene, polyethylene, polystyrene,polyvinyl chloride, polytetrafluoroethylene, polysulfone, celluloseacetate, polymethylmethacrylate, polyethylene, and polyvinylacetate.

The electrical signal generator 110 may be programmed with an externalcomputer 150 using programming software of the type copyrighted by theassignee of the instant application with the Register of Copyrights,Library of Congress, or other suitable software based on the descriptionherein, and a programming wand 155 to facilitate radio frequency (RF)communication between the computer 150 and the signal generator 110. Thewand 155 and software permit non-invasive communication with thegenerator 110 after the latter is implanted, according to means known inthe art.

A variety of stimulation therapies may be provided in implantablemedical systems 100 of the present invention. Different types of nervefibers (e.g., A, B, and C fibers being different fibers targeted forstimulation) have different conduction velocities and stimulationthresholds and, therefore, differ in their responsiveness tostimulation. Certain pulses of an electrical stimulation signal, forexample, may be below the stimulation threshold for a particular fiberand, therefore, may generate no action potential in the fiber. Thus,smaller or narrower pulses may be used to avoid stimulation of certainnerve fibers (such as C fibers) and target other nerve fibers (such as Aand/or B fibers, which generally have lower stimulation thresholds andhigher conduction velocities than C fibers). Additionally, techniquessuch as pre-polarization may be employed wherein particular nerveregions may be polarized before a more robust stimulation is delivered,which may better accommodate particular electrode materials.Furthermore, opposing polarity phases separated by a zero current phasemay be used to excite particular axons or postpone nerve fatigue duringlong term stimulation.

Turning now to FIG. 2, a stylized isometric illustration of a helicalelectrode assembly 210 in accordance with one embodiment of the presentinvention is illustrated. The electrode assembly may be formed into ahelical configuration and may be made of a flexible material, such as asilicone polymer substrate with semiconductor layers imprinted thereonusing photolithography techniques. The electrode assembly may alsocomprise an end member 220 that provides an interface to a lead wire inelectrical communication with the IMD. The helical structure of FIG. 2may be wrapped around a portion of the patient's body, such as a nerve,e.g., the vagus nerve, and anchored thereupon.

Turning now to FIG. 3, another isometric depiction of the electrodeassembly 210, in accordance with one illustrative embodiment of thepresent invention, is provided. An electrode 330 may be formed on thesurface of the inside portion of the electrode assembly 210. Theelectrode assembly 210 may be wrapped around a target portion of thepatient's body, e.g., a nerve, such that the electrode 330 contacts thetarget portion at a predetermined location. The electrode 330illustrated in FIG. 3 may comprise a plurality of electrodes formed onthe inside surface of various portions of the electrode assembly 210.The electrodes 300 may comprise a conductive material such as platinum,iridium, and/or platinum/iridium alloys and/or oxides. Further detailsas to the position of the electrodes on the electrode assembly 210 areprovided in subsequent drawings and accompanying description below.

Turning now to FIG. 4, a stylized depiction is provided of the electrodeassembly 210 during fabrication in accordance with an embodiment of thepresent invention. The electrode assembly 210 comprises a substratematerial on which various electrodes may be formed. Flexible substratematerials 440 upon which a plurality of electrodes may be formed maycomprise various materials, such as silicone rubbers, siloxane polymers,and other materials previously noted.

Various conductive structures in a variety of manners may be formed uponthe flexible material 440. The conductive structures may include one ormore electrodes 410, which are capable of being in contact with aportion of a patient's body, e.g., a nerve, and provide an electricalsignal from the signal generator 110 or detect electrical signals in thepatient's body. The conductive structures may also include variousconductive strips 420 and a plurality of connection pads 430. Each ofthe electrodes 410 may be respectively coupled electrically to one of aplurality of conductive strips 420 that are capable of carryingelectrical signals to or from the electrodes 410. Further, each of theconductive strips 420 may be respectively coupled electrically to one ofthe plurality of connection pads 430. The connection pads 430 may thenbe used as an interface to a wire or a lead structure that may containseveral electrical components that may each respectively attach orconnect to the set of connection pads 430 illustrated in FIG. 4.

Connection pads 430 may be formed at the edge of the helical structureor on the end portion 220 of FIG. 2. In one embodiment, the end portion220 may be part of the flexible material 440 (as depicted in FIG. 4),upon which various processes described herein may be used to form theconnection pads 430. In an alternative embodiment, the end portion 220may be a separate structure that is coupled to the helical structure, asindicated in FIGS. 2 and 3. The end portion may house a plurality ofconnection pads 410. Continuing referring to FIG. 4, in one embodiment,the portion of the flexible material 440 that contains the electrodes410 may be shaped into a helical form, while the portion of the flexiblematerial 440 that comprises the conductive strips 420 may be shaped intoan undulated form, and the portion of the flexible material 440 thatcomprises the connection pads 430 may formed in a generally flatconfiguration. In this manner, a connector may be coupled to theconnection pads 430, wherein a lead assembly that comprises a pluralityof electrical wires may be operatively coupled to connection pads 430.Therefore, electrical connections between a plurality of electricalwires in a lead assembly may be respectively operatively coupled to aplurality of electrodes 410.

Various methods may be used to form the conductive elements illustratedin FIG. 4 upon the flexible material 440 in a flat or generally planarinitial configuration. Semiconductor processing techniques, such asphotolithography processes, copper deposition processes, single and/ordual damascene processes, etc., known to those skilled in the art havingbenefit of the present disclosure, may be employed to form theconductive structures (e.g., 410, 420, 430) upon the flexible material440. The flexible material 440 may then be formed into a helicalstructure, wherein the electrodes 410 are located on an inner surface ofthe helical structure such that the electrodes would be in electricalcommunication with a patient's body when the electrode assembly 210 iswrapped around a target structure.

In one embodiment, the flexible material 440 is formed into a helicalstructure after creating conductive structures 410, 420, 430, e.g., onthe material 440 while the material 440 is in a flat or generally planarconfiguration. The flat substrate material 440 is then formed into ahelical configuration. In an alternative embodiment, the flexiblematerial 440 is first formed into a helical structure, which is thenunfurled into a flat or generally planar configuration. The conductivestructures are then created on the unfurled, flat material, andthereafter a restraining force on the unfurled structure is released toallow it to return to a helical configuration. Further, a portion of theflexible material 440 may be shaped in an undulated form. In oneembodiment, a portion of the flexible material 440 that comprisesconductive structures may be shaped into an undulated form. Knownfabrication techniques may be used to form the flexible material into ahelical structure and/or into an undulated structure, such as heattreating and/or annealing techniques, and scoring and/or etchingportions of the substrate to urge the substrate into a helicalconfiguration.

Turning now to FIG. 5, a flowchart associated with a method forproviding the electrode assembly 210 in accordance with an illustrativeembodiment of the present invention, is provided. Initially, a substrateis provided comprising a flexible material (block 605). In oneembodiment, the substrate is generally flat. In another embodiment, thesubstrate is generally planar. A base layer or first layer may be formedon the substrate that is part of the flexible material 440 of FIG. 4(block 610). Numerous types of deposition techniques known to thoseskilled in the art having benefit of the present disclosure may be usedto generate the base layer. Such techniques may include, withoutlimitation, chemical plating, plasma ion deposition, vapor depositionand sputtering. In one embodiment, the base layer is a substantiallynon-conductive film of material, such as a dielectric material.

A conductive structure may then be formed over the first layer to form asecond layer (block 620). The conductive structure may include theelectrode 410, the conductive strip 420, the connection pads 430, etc.Various techniques may be used to form the conductive structures on thesecond layer. The formation of the conductive structure may includevarious semiconductor processing steps, such as performing aphotolithography process (block 622). The photolithography process mayuse a mask and a light source to provide for deposition of material in apredetermined desired formation to form one or more electrodes 410,conductive strips 420, and/or connection pads 420. An etch process mayalso be performed on the second layer (block 624). The etch process maybe used to etch away excessive deposition material in order to conformthe various conductive structures into predetermined shapes and sizes.In one embodiment, an excimer laser may be used to remove excessivedeposition material, e.g., removing excessive polymer depositionmaterial to expose a precisely defined surface area for an electrode410. For example, the dimensions of the electrode may be preciselycontrolled to provide a width of from about 0.1 mm to about 2.0 mm, witha typical width of about 1.0 mm, and a length of from about 0.1 mm toabout 10 mm, typically about 7 mm. The widths of the conductive stripsmay range from about 20 μm to about 100 μm (0.1 mm), with lengthsthereof varying as necessary for a particular application. Theconnection pads may be provided with dimensions sufficient to allow goodelectrical connection to a lead wire, which will vary according theapplication. In one embodiment, the connection pads may be provided withmajor dimensions ranging from about 20 μm to about 3 mm. Further, achemical-mechanical polishing (CMP) process may also be performed on thesecond layer (block 626). Various semiconductor processing techniquesmay be performed to form the conductive structures over the first layer.Alternatively, a copper deposition process, such as a damascene processor a dual damascene process, may be performed to form the conductivestructures on the second layer (block 628).

Upon forming one or more conductive structures on the second layer, anon-conductive layer may then be formed over the second layer, resultingin a third layer (block 630). Another set of conductive structures maythen be formed over the third layer to form the fourth layer thatcontains additional conductive structures (block 640). This set ofprocesses (i.e., forming alternating non-conducting and conductinglayers) may then be repeated until a desired number of electrodes, aswell as associated conductive strips and connection pads, are formed onthe flexible material 440 (block 650). Additionally, upon completion ofthe formation of the conductive portions on the flexible material,additional coating steps may be performed. The coating steps may includecoating the electrode assembly with a non-conductive, flexible coatingwhile masking off the electrodes. Optionally, a lead assembly having aplurality of lead elements may be provided, and the lead elements may becoupled to the electrodes using the connection pads (block 660). In thismanner, an electrode assembly 210 with a helical electrode portioncomprising a plurality of electrodes, conductive strips, and connectionpads is provided. The electrode assembly may be coupled to a leadassembly, which may have an undulated form, using the connection pads.At least a portion of the substrate may be formed into a helical shape(block 670). In one embodiment, the portion of the substrate containingthe electrodes may be formed into a helical shape.

Turning now to FIG. 6, a stylized depiction of the electrode assembly ofthe present invention in a staggered, multi-layered configuration isprovided in accordance with an illustrative embodiment of the presentinvention. The flexible material 440 may comprise a first layer uponwhich a first electrode 710 and an associated conductive strip 720 areformed into a second layer using the various techniques described above.The conductive strip runs along at least a portion of the length of theflexible material 440 and is illustrated as dotted lines undersubsequent layers that are formed on the connector strip 440, such as athird layer, and a fourth layer.

Upon forming of the first layer and the second layer (which includes thefirst electrode 710 at a predetermined location, and associatedconductive strip 720 that runs along the length of the flexible material440), a third layer is formed. The third layer is formed at an offsetposition on the second layer such that the third layer does not overlapthe region in which the first electrode 710 resides. Upon the thirdlayer, a fourth layer comprising a second electrode 730 and anassociated second conductive strip 740 may be formed. The secondconductive strip 740 may run along a portion of the length of theflexible material 440.

Further, offset slightly from the third and fourth layers, a fifth layermay be formed over the fourth layer. The fifth layer does not overlapthe portion of the first and second or third and fourth layers uponwhich first electrode 710 or the second electrode 730 reside. Upon thefifth layer, sixth layer comprising a third electrode 750 and anassociated third conductive strip 760 are formed. The third conductivestrip 760 runs along a portion of the length of the flexible material440. In this manner, a “stair step” of layers that contain electrodesand conductive strips are generated on a single flexible material 440until a desired number of electrodes are formed. Further, each layerupon which an electrode is formed may also contain a respectiveconnection pad for coupling the electrode and its associated conductivestrip to a lead element.

Upon forming the flexible material 440 into a helical structure, andsubsequently wrapping the helical structure around a portion of thepatient's body, such as a nerve, the first through third electrodes 710,730, 750, come into contact with respective portions of the patient'sbody without contacting the conductive strips 720, 740, 760 associatedwith another electrode. Different electrical signals can be applied todifferent regions of the patient's body. Further, the first electrode710 may deliver a therapeutic stimulation signal, whereas the secondelectrode 730 may acquire resultant electrical data, e.g., by sensingthe activity on the nerve. In this manner, the IMD is capable ofindependently controlling the electrical activities of each of theelectrodes.

Referring simultaneously to FIGS. 7 and 8, a stylized side view of theflexible material 440 upon which the first through sixth layers areformed, is illustrated in FIG. 7. FIG. 8 illustrates the first througheighth layers that are formed above the substrate on the flexiblematerial 440. As depicted in FIG. 7, a first layer is formed above thesubstrate. Above the first layer, the second layer comprising the firstelectrode 710 and the first conductive strip 720 are formed. Withoutoverlapping the first electrode 710, the third layer is formed uponwhich the fourth layer comprising the second electrode 730 and thesecond conductor strip 740 are formed. The third layer is capable ofelectrically isolating the conductive structures in the second layer.Similarly, upon forming the conductive structures into a fourth layerabove the third layer, the fifth layer is formed above a portion of theconductive strip portion of the third and fourth layers withoutoverlapping the second electrode 730. Upon the fifth layer, a sixthlayer comprising the third electrode 750 and the associated thirdconductive strip 730 are formed. Therefore, the thickness of the overallelectrode assembly 210 will depend on the number of electrodes that areformed on the flexible material 440. In this manner, each of the firstthrough third electrodes 710, 730, 750, or additional electrodes thatmay be formed on the flexible material 440, operate independently.Although only six layers and three electrodes are illustrated forclarity and ease of description, those skilled in the art having benefitof the present invention would readily appreciate that variousadditional layers may be similarly added and remain within the spiritand scope of the present invention.

Referring to FIG. 9, an alternative embodiment of providing theelectrode assembly in accordance with one alternative illustrativeembodiment of the present invention, is provided. FIG. 8 illustrates asubstrate associated with the flexible material 440. Upon the substrate,a first layer may be formed. Upon the first layer, a second layercomprising a first conductive strip 920 is formed. The first conductivestrip 920 may be connected to a corresponding electrode that will beformed on another layer.

Subsequently, a third layer is formed above the first and second layers.The third layer overlaps the first layer as well as the first conductivestrip 920 which comprises the second layer. A channel may be groovedinto the second layer to provide for the formation of a first via 915. Afourth layer comprising a second conductive strip 920 is formed abovethe third layer to be connected to a corresponding electrode to beformed on a subsequent layer. Subsequently, a fifth, non-conductivelayer is formed above the conductive fourth layer. The fifth layer mayalso comprise a groove formation to accommodate the first via 915 aswell as a second via 935 to be formed. Further, a sixth layer,comprising a third conductive strip 960 for electrical coupling with acorresponding electrode. A seventh, non-conductive layer is formed abovethis sixth layer. Three grooves are formed in the seventh layer toaccommodate the first via 915, the second via 935 and a third via 955 tobe formed.

Upon the seventh layer, a first electrode 910, a second electrode 930,and a third electrode 950 are formed. However, before the formation ofthe first through third electrodes, 910, 930, 950, corresponding vias915, 935, 955 are formed. The first via 915 that interconnect the firstelectrode 910 to the first conductive strip 920 is formed above thesecond layer and into the grooves that already exist in all of thelayers below the electrode. Similarly, the second via 935 is formed overthe fourth layer to interconnect the second electrode 930 with thesecond conductive strip 940. Further, the third via 955 is formed abovethe sixth layer and in the grooves of the layers below the thirdelectrode. The third via 955 is capable of connecting the thirdelectrode 950 to the third conductive strip 960. Therefore, all threeelectrodes 910, 930, 950, are respectively electrically coupled to thecorresponding conductive strips 920, 940, 960. Further, similartechniques may be used to generate corresponding connection pads thatinterconnect each electrode to the connection pads for electricalcommunications with an IMD.

The surface of the electrode assembly 210 only exposes conductiveelectrodes that come into contact with a portion of the patient's body,therefore, independent signals may be sent to and from the electrodes910, 930, 950 via the electrode assembly 210. In this manner, staggeringof the time period relating to the delivery of stimulation signal ismade possible. Further, independent acquisition of biometric data anddelivery of an electrical signal may be performed substantiallysimultaneously. Utilizing the structure described in FIG. 9, theelectrodes 910, 930, 950 are capable of operating independently.Although only three electrodes are illustrated in FIG. 9, those skilledin the art would appreciate that any number of electrodes may beimplemented using the technique disclosed in FIG. 9 while stillremaining within the spirit and scope of the present invention.

Utilizing embodiments of the present invention, an electrode assemblythat comprises an array of electrodes may be deployed to perform varioustherapy delivery functions and/or sensing functions. Therefore, currentsteering and targeted delivery of therapeutic electrical signals todifferent portions of a particular nerve may be performed using themulti-electrode assembly described by embodiments of the presentinvention. Additionally, electrode assemblies provided by theembodiments of the present invention may be manufactured in a moreuniform, dimensionally-controlled, and efficient manner utilizingprocess methods described herein and known to those skilled in the artof semiconductor manufacturing having benefit of the present disclosure.Embodiments of the present invention provides for more effective therapyand greater efficacy while delivering targeted therapy delivery tovarious portions of the patient's body.

All of the methods and apparatus disclosed and claimed herein may bemade and executed without undue experimentation in light of the presentdisclosure. While the methods and apparatus of this invention have beendescribed in terms of particular embodiments, it will be apparent tothose skilled in the art that variations may be applied to the methodsand apparatus and in the steps or in the sequence of steps of themethods described herein without departing from the concept, spirit, andscope of the invention, as defined by the appended claims. It should beespecially apparent that the principles of the invention may be appliedto selected cranial nerves other than the vagus nerve to achieveparticular results.

The particular embodiments disclosed above are illustrative only as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown other than as describedin the claims below. It is, therefore, evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

1. An electrode assembly for conducting a first electrical signalbetween an implantable medical device and a target tissue, comprising: ahelical member; a first electrode and a second electrode formed uponsaid helical member, said first and second electrodes to deliver saidfirst electrical signal; a first conductive element formed upon saidhelical member and operatively coupled to said first electrode, saidfirst conductive element to carry said first electrical signal to saidfirst electrode; and a second conductive element formed upon saidhelical member and operatively coupled to said second electrode.
 2. Theelectrode assembly of claim 1, wherein said first and second conductiveelements are conductive wires that are positioned in at least apartially parallel configuration along the length of at least a portionof said helical member.
 3. The electrode assembly of claim 1, furthercomprising a third electrode formed upon said helical member, whereinsaid first, second, and third electrodes form an electrode array.
 4. Theelectrode assembly of claim 3, wherein said first electrode is adaptedto carry said first electrical signal, said second electrode is adaptedto carry a second electrical signal different from said first electricalsignal, and said third electrode is adapted to carry a third electricalsignal different from said first and second electrical signals.
 5. Theelectrode assembly of claim 1, further comprising a first lead wireoperatively coupled to said first conductive element and a second leadwire operatively coupled to said second conductive element.
 6. Theelectrode assembly of claim 5, further comprising a lead interfaceoperatively coupled to said helical member, said first and second leadwires being operatively coupled to said first and second conductiveelements via said lead interface.
 7. The electrode assembly of claim 1,wherein said first electrode and said second electrode comprise anelectrode pair, and wherein said electrode pair is a sensing electrodeadapted to sense electrical activity in a target tissue.
 8. Theelectrode assembly of claim 1, wherein said helical material comprises amaterial selected from the group consisting of siloxane polymers,polydimethylsiloxanes, silicone rubbers, polyurethane, polyetherurethane, polyetherurethane urea, polyesterurethane, polyamide,polycarbonate, polyester, polypropylene, polyethylene, polystyrene,polyvinyl chloride, polytetrafluoroethylene, polysulfone, celluloseacetate, polymethylmethacrylate, polyethylene, and polyvinylacetate, andsaid first and second electrodes comprises a material selected from thegroup consisting of platinum, iridium, and platinum/iridium alloys. 9.The electrode assembly of claim 1, wherein said first conductive elementcomprises a first conductive strip and a first conductive interface, andsaid second conductive element comprises a second conductive strip and asecond conductive interface.
 10. The electrode assembly of claim 1,wherein said helical member further comprises a at least a thirdelectrode operatively coupled to a third conductive element.
 11. Theelectrode assembly of claim 1, wherein said helical member is capable ofbeing wrapped around a nerve, wherein said first and second electrodescome into electrical contact with said nerve to deliver a stimulationsignal in a cascading manner.
 12. The electrode assembly of claim 1,wherein said first electrical signal is delivered to said first andsecond electrodes, said helical member further comprises a thirdelectrode operatively coupled to a third conductor, a fourth electrodeoperatively coupled to a fourth conductor, and wherein a secondelectrical signal is delivered to said third and fourth electrodes. 13.The electrode assembly of claim 1, wherein said first electrode islocated at a first position on the helical member and said secondelectrode is located at a second position on the helical member.
 14. Amethod for forming a helical electrode assembly for carrying anelectrical signal associated with an implantable medical device,comprising: forming a first layer on a generally flat substrate; forminga first conducting structure as a second layer upon said first layer,said first conducting structure comprising a first electrode and a firstconductive strip operatively coupled to said first electrode; forming athird, non-conductive layer above said first and second layers; forminga second conducting structure as a fourth layer upon said third layer,said second conducting structure comprising a second electrode and asecond conductive strip operatively coupled to said second electrode;and forming said generally flat substrate into a helical structure. 15.The method of claim 14, wherein forming said first and second conductingstructures comprises: performing a photolithography process to imprintsaid first conducting structure upon said first layer and said secondconducting structure upon said third layer; and performing an etchprocess to control at least one dimension relating to each of said firstand second conducting structures within respective predeterminedtolerances.
 16. The method of claim 15, further comprising performing achemical-mechanical polishing process.
 17. The method of claim 14,further comprising forming a fifth, non-conducting layer above saidthird and fourth layers, and forming a third conducting structure as asixth layer upon said fifth layer, said third conducting structurecomprising a third electrode and a third conductive strip operativelycoupled to said third electrode, wherein forming said fifth layercomprises performing a deposition process.
 18. The method of claim 14,wherein forming said first and second conducting structures comprises:performing a metal deposition process to deposit a conductive materialfor forming said first and second conducting structures; and performingan etch process to control at least one dimension relating to each ofsaid first and second conducting structures within predeterminedtolerances.
 19. The method of claim 14, wherein forming said first andsecond conducting structures comprises offsetting said first conductingstructure from said second conducting structure such that said first andsecond electrodes are exposed on the surface of said electrode assembly.20. The method of claim 14, further comprising: forming a fifth,non-conducting layer above said third and fourth layers, and forming athird conducting structure as a sixth layer upon said fifth layer, saidthird conducting structure comprising a third electrode and a thirdconducting strip operatively coupled to said third electrode; andforming a seventh non-conducting layer above said fifth and sixthlayers, and forming a fourth conducting structure as an eighth layerupon said seventh layer, said fourth conducting structure comprising afourth electrode and a fourth conducting strip operatively coupled tosaid fourth electrode.
 21. The method of claim 14, further comprising:forming a first connection pad on the surface of said electrodeassembly, said first connection pad being electrically coupled to saidfirst conductive strip; and forming a second connection pad on thesurface of said electrode assembly, said second connection pad beingelectrically coupled to said second conductive strip.
 22. The method ofclaim 14, further comprising: forming a first via to electrically couplesaid first conductive strip to said first electrode; and forming asecond via to electrically couple said second conductive strip to saidsecond electrode.
 23. A method for forming a helical electrode assemblyfor carrying a signal associated with an implantable medical device,comprising: forming a first layer on a generally flat substrate; forminga first conducting structure and a second conducting structure upon saidfirst layer, said first conducting structure comprising a firstelectrode and a first conductive strip operatively coupled to said firstelectrode, and said second conducting structure comprising a secondelectrode and a second conducting strip operatively coupled to saidsecond electrode; forming a second, non-conductive layer such that saidfirst and second conductive strips are substantially covered by saidsecond layer and said first and second electrodes remain exposed; andforming said generally flat substrate and first and second layers into ahelical structure.
 24. An implantable medical system for providing atherapeutic electrical signal to a target tissue using a helicalelectrode assembly, comprising: an implantable medical device forgenerating a therapeutic electrical signal; a lead assembly operativelycoupled to said implantable medical device and adapted to carry saidtherapeutic electrical signal, said lead assembly comprising first andsecond lead elements; and an electrode assembly operatively coupled tosaid lead assembly and adapted to deliver said therapeutic electricalsignal to a target tissue, said electrode assembly comprising: a helicalmember; a first electrode and a second electrode formed upon saidhelical member; a first conductive element formed upon said helicalmember and operatively coupled to said first electrode and to said firstlead element; and a second conductive element formed upon said helicalmember and operatively coupled to said second electrode and to saidsecond lead element.